No abstract

Coordination polymer coated mesoporous silica nanoparticles for drug delivery are successfully synthesized. The system ensures that drugs are stored in the mesopores under a physiological environment. Upon H(+) stimulus in the endosomal and lysosomal compartments, the drugs are released into the intracellular organelles of cancer cells, effectively killing the cells.

The optical chirality induced at the absorption bands due to electronic exciton coupling of the transition dipole moments between chromophores in close proximity is ubiquitous in helical organic materials. However, inorganic materials with optical activity resulting from electronic transitions have not been explored. Here we report the synthesis of chiral TiO2 fibres via transcription of the helical structure of amino acid-derived amphiphile fibres through coordination bonding interactions between the organics and the TiO2 source. Upon calcination, the as-prepared amorphous TiO2 double-helical fibres with a pitch length of ~100 nm were converted to double-helical crystalline fibres with stacks of anatase nanocrystals in an epitaxial helical relationship. Both the amorphous and anatase crystalline helical TiO2 fibres exhibited optical response to circularly polarized light at the absorption edge around ~350 nm. This was attributed to the semiconductor TiO2-based electronic transitions from the valence band to the conduction band under an asymmetric electric field.

Helical symmetry can be found in most flowers with a rotation of contort petal aestivation. For micro- and nanoscale analogies, flower mimicking structures have been reproduced; however, the conceptual chirality of "nanoflowers" has not yet been defined. Here, the chirality of the "flower" was defined by its nanosized chiral structure and consequent optical activity (OA), opening new horizons for the physical theory and chiral materials. We report the surfactant-mediated hydrothermal synthesis of chiral CuO nanoflowers using sodium dodecyl sulfate (SDS) as a structure-directing agent, an amino alcohol as a symmetry-breaking agent, and cupric salt as the inorganic source. Two levels of hierarchical chirality exist for a CuO nanoflower including primary helically arranged "nanoflakes" and secondary helical "subnanopetals" that form "nanopetals". The nanoflowers exhibited a prominent optical response to circularly polarized light (CPL) at the absorption bands characteristic of CuO.

A macroporous silica with azimuthally shifted double-diamond frameworks has been synthesized by the self-assembly of an amphiphilic ABC triblock terpolymer poly(tert-butyl acrylate)-b-polystyrene-b-poly(ethylene oxide) and silica source in a mixture of tetrahydrofuran and water. The structure of the macroporous silica consists of a porous system separated by two sets of hollow double-diamond frameworks shifted 0.25c along ⟨001⟩ and adhered to each other crystallographically due to the loss of the mutual support in the unique synthesis, forming a tetragonal structure (space group I4 1 /amd). The unit cell parameter was changed from a = 168 to ∼240 nm with c = √2a by tuning the synthesis condition and the wide edge of the macropore size was ∼100 to ∼140 nm. Electron crystallography was applied to solve the structure. Our studies demonstrate electron crystallography is the only way to solve the complex structure in such length scale. Besides, this structure exhibits structural color that ranged from violet to blue from different directions with the bandgap in the visible wavelength range, which is attributed to the structural feature of the adhered frameworks that have lower symmetry. Calculations demonstrate that this is a new type of photonic structure. A complete gap can be obtained with a minimum dielectric contrast of 4.6, which is inferior to the single diamond but superior to the single gyroid structure. A multilayer core−shell bicontinuous microphase templating route was speculated for the formation of the unique macroporous structure, in which common solvent tetrahydrofuran in hydrophobic shell and selective solvent water in hydrophilic core to enlarge each microphase sizes.